874 Part V / Movement
Figure 35–12 A parietal neuron is active before memory-
guided saccades.Traces are aligned at events indicated by
vertical lines. (Adapted, with permission, from Powell and
Goldberg 2000.)
A.The monkey plans a saccade from a fixation point to a target
in the receptive field of a neuron in the lateral intraparietal cor-
tex. The neuron responds to the appearance of the target (1).
It continues to fire after the target has disappeared but before
the signal to make the saccade and stops firing after the onset
of the saccade (2).
B.The monkey plans a saccade to a target outside the
receptive field. The neuron responds initially to a distractor
in the receptive field as strongly as it did to the target of a
saccade.
noticeable. Saccadic eye movements and visual atten-
tion are closely intertwined (Figure 35–5).
The lateral intraparietal area in the monkey is
important in the generation of both visual attention
and saccades. The role of this area in the processing of
eye movements is best illustrated by a memory-guided
saccade. To demonstrate this saccade, a monkey first
fixates a spot of light. An object (the stimulus) appears
in the receptive field of a neuron and then disappears;
then the spot of light is extinguished. After a delay, the
monkey must make a saccade to the former location of
the vanished object. Neurons in the lateral intrapari-
etal area respond from the moment the object appears
and continue firing after the object has vanished and
throughout the delay until the saccade begins (Figure
35–12A), but their activity can be also dissociated from
saccade planning. If the monkey is planning a saccade
目标
干扰项
目标
12
外侧顶内
神经元的记录
A 神经元从目标出现一直激活到扫视 B
神经元在感受野中对干扰项的响应同样强烈
100
脉冲
/秒
100
脉冲
/秒
100 毫秒
100 毫秒
干扰项
目标
目标
注视点
扫视
扫视
感受野
to a target outside the receptive field of a neuron and a
distractor appears in the field during the delay period,
the neuron responds as vigorously to the distractor as
it does to the target of a saccade (Figure 35–12B).
Lesioning of a monkey’s posterior parietal cortex,
which includes the lateral intraparietal area, increases
the latency of saccades and reduces their accuracy.
Such a lesion also produces selective neglect: A mon-
key with a unilateral parietal lesion preferentially
attends to stimuli in the ipsilateral visual hemifield.
In humans as well, parietal lesions—especially right
parietal lesions—initially cause dramatic attentional
deficits. Patients act as if the objects in the neglected
field do not exist, and they have difficulty making eye
movements into that field (Chapter 59).
Patients with Balint syndrome, which is usually
the result of bilateral lesions of the posterior parietal
Kandel-Ch35_0860-0882.indd 874 20/01/21 11:20 AM